Mechanical end face seal assemblies for sealing rotating shafts such as those found, for example, between the impeller shaft and the housing of a pump, are known. In some applications, such seal assemblies are installed, replaced, and serviced in the field where the free end of the rotatable shaft is not accessible, for example, because it is connected to a motor or another prime mover operating the rotatable shaft.
To enable the installation, service, or replacement of sealing components in these environments, fully split mechanical end face seal arrangements have been created. These fully split mechanical end face seal arrangements typically include two split, relatively rotating, seal face defining rings. The rings have sliding radial faces arranged in facing, sealing relation. One of the rings, typically axially stationary, is referred to as the mating ring. It may be connected to the rotating shaft and configured to rotate with it. The second ring, which is axially movable, commonly referred to as the primary ring, may be contained in a stationary housing in the form of a gland plate surrounding the shaft where it exits the housing. The two rings are brought into contact with one another by an axial preload component to provide a sliding seal between the relatively rotating faces. The mating and primary seal rings as well as all associated surrounding and supporting components are split, typically in a diametrical fashion, to enable installation around the rotatable shaft without the need for access to the free end of the shaft.
Examples of known fully split seal configurations can be seen in U.S. Pat. Nos. 5,662,340; 5,961,122; 6,485,023 and others. Such seals include split seal face defining rings in semi-circular segments, associated semi-circular carriers for the primary and mating rings, secondary seals, usually elastomeric rings or strips between the rings and carriers, and a preloading element of semi-circular segments which axially urges the primary ring into facing sealing relation with the axially stationary mating ring. The seal components are disposed within a gland plate secured to the housing in surrounding relation to the shaft and provide the fluid sealing function.
The components including the mating and primary seal face defining rings are diametrically split into halves or segments. The seal face defining ring halves are typically preassembled into carriers, sometimes referred to as adapters, that retain the face defining ring segments until the seal arrangement is installed and secured to the rotatable shaft and to the housing. Commonly, pins, connected to the carriers, prevent the ring halves from falling out of the associated carrier before, and during installation and completion of the assembly process.
Even though the above-mentioned examples of split seal assemblies are effective in providing a seal arrangement that can be assembled around a shaft without access to the free end of the shaft they suffer from certain important drawbacks. One such drawback is the need for the use of adhesive to retain the various resilient elastomeric seal elements in place prior to completion of installation and assembly of the split mechanical end face seal assembly between a housing and shaft. Another is the inability of the installer to visually inspect the face contact between the two face defining seal rings during installation. The incorporation of the seal ring halves into cartridges results in the sealing engagement of the ring seals being concealed from view during installation.
Additionally, the known designs rely on the proper, final positioning of each seal ring segment relative to the assembled cartridge to occur during installation as the cartridges are placed around the rotatable shaft and the two halves joined together. While the proper positioning of the rings under such conditions is typically likely, any intrusion of debris between the seal ring segment and its cartridge that goes unnoticed by the installer may cause misalignments in the finished seal assembly, which may affect performance and durability.
It is also the case in existing split mechanical end face seal assemblies having pre-assembled components such as mating ring carrier segments with attached mating ring segments and primary ring carrier segments with attached primary ring segments in which the seal ring segments are rigidly supported within their respective carriers. Thus, the advantages derived from axial non-rigid support of the seal face defining segments are not attainable.